The Cellular Basis 



127 



FIG. 41 



organism, is fundamental in all modern studies of heredity. It was 

 especially emphasized by Weismann . in his germplasm theory 

 and recently it has been made prominent by Johannsen under the 

 terms "genotype" and "phenotype" ; the genotype is the funda- 

 mental hereditary constitution of an organism, it is the germinal 

 type; the phenotype is the developed organism with all of its 

 visible characters, it is the somatic type. 



But important as this distinction is between germ and soma 

 it has sometimes been overemphasized. This is one of the chief 

 faults of Weismann's theory. The germ and the soma are generi- 

 cally alike, but specifically different. Both germ cells and somatic 

 cells have come from the same oosperm, but have differentiated in 

 different ways ; the tissue cells have lost certain things which the 

 germ cells retain and have developed other things which remain 

 undeveloped in the germ cells. But the germ cells do not remain 



